JP2006249335A - Water-based ink, water-based ink set and ink-jet recording method, ink cartridge recording unit and recording device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water-based ink that can reduce the carbon black content in forming an image on glossy or semi-glossy paper, can suppress the microbeading phenomenon caused when a monochromatic image is formed by using the water-based light black ink including a nonionic surfactant for improving the penetrability and can achieve good fixing property. <P>SOLUTION: The water-based ink includes 0.2 to 1.5 mass% of carbon black and 0.5 to 3.0 mass% of a nonionic surfactant, further includes at least one of water-soluble organic compound that is solid at 25°C in the simple form and a water-soluble organic compound that is liquid at 25°C in the simple form and has a surface tension of more than 35 mN/m in the simple form wherein the total amount of the water-soluble organic compound is 30 to 40 mass% in the ink and the surface tension of the water-soluble organic compound is lower than 35 mNn at 25°C in the simple form. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a water-based ink containing a relatively small amount of carbon black, a water-based ink set in which the water-based ink is combined, an ink jet recording method, an ink cartridge, a recording unit, and a recording apparatus using the same. About.

  In the ink jet recording method, recording is performed by ejecting small ink droplets and attaching the ink to a recording medium (recording material) such as paper. In particular, according to an ink jet recording method (thermal ink jet recording method) in which an electrothermal transducer is used as the discharge energy supply means and droplets are generated by generating bubbles by applying thermal energy to the ink, the recording head is used. High-density multi-orifice can be easily realized, and high-resolution and high-quality images can be recorded at high speed (see Patent Documents 1 to 3).

  In recent years, there has been a demand for inks that can be used in various applications using these technologies. In particular, pigment inks that use pigments as colorants are used in applications that emphasize image fastness. Even in the use of these pigment inks, it is required not only to form a beautiful colored image, but also to form a gradation and a halftone of a monochrome image beautifully.

  In order to satisfy these requirements, the use of multiple black inks with different carbon black densities improves the color reproducibility and darkness of dark colors such as shadow areas, the stability of gray balance, and metamerism. Has been proposed (see Patent Documents 4 and 5). Hereinafter, among a plurality of black inks having different carbon black concentrations, a black ink having a relatively low carbon black content in the ink is referred to as a light black ink.

  In addition, some problems in the case where an image is formed using black ink and light black ink, and a solution to the problem have been proposed. For example, an ink set has been proposed in which the surface tension of light black ink is made lower than the surface tension of black ink for the purpose of improving ink permeability and fixability. A surfactant is used to adjust the surface tension of the ink at that time (see Patent Document 6). In addition, for the purpose of improving the color developability and abrasion resistance of an image, it has been proposed that polymer fine particles are contained only in an ink having a small color material content (see Patent Document 7). Furthermore, for the purpose of suppressing the occurrence of color bleeding, feathering, and color bleeding in an image, it has been proposed that at least one of the inks having a low color material content contains saccharides (see Patent Document 8). ).

  In addition, at least three or more kinds of densities are used for the purpose of reducing reddishness and yellowishness of the image, reduction of golden gloss phenomenon, phase shift, and further stability of gray balance and metamerism (color matching conditions). Proposals have been made using different black inks as a set (see Patent Documents 9 to 12). Furthermore, in the proposal that added two or more kinds of light black inks, light cyan and light magenta were added to the ink used in combination with other colorants in addition to carbon black in the ink formation. By using an ink set, an ink set with each of the red, green, violet, and orange inks added, or an ink set with a resin emulsion added to the ink, an effect of improving the above-described problems related to the color and hue can be obtained. It is stated that.

Japanese Patent Publication No. 61-59911 Japanese Patent Publication No. 61-59912 Japanese Examined Patent Publication No. 61-59914 Japanese Patent Laid-Open No. 11-48502 JP 2001-288390 A Japanese Patent Laid-Open No. 2001-179956 JP 2002-003768 A JP 2003-277653 A JP 2004-027127 A JP 2004-099657 A JP 2004-225036 A JP 2004-250519 A

  In the process of studying the case where the light black ink whose pigment is carbon black is used, the present inventors have found that the aggregated state of the pigment after being applied to the recording material is the water-soluble organic contained in the ink. The inventor has obtained the knowledge that it greatly depends on the characteristics of the solvent and the change of the printing process, and this causes a new problem that becomes a problem in forming a high-quality image. Specifically, a single-color image is formed on glossy or semi-glossy paper using light black ink, which is used in the above-mentioned technology and has a relatively low carbon black content and contains a surfactant. In this case, when the dots are connected finely, and the ink dots are in a state of having fluidity before being fixed on the ink receiving layer of glossy paper or semi-glossy paper, the ink dots are formed in the ink receiving layer. Irregularly moving in the surface direction of the surface, adjacent dots and dots that subsequently land form an aggregate, and the formed recorded image has density unevenness that can be confirmed with the naked eye as shown in FIG. Recognized that a new phenomenon occurs. Hereinafter, this phenomenon is referred to as a microbeading phenomenon. This micro beading phenomenon is a phenomenon that occurs when printing is performed at a relatively low duty. When printing is performed at a high duty during multi-pass printing using a conventional pigment black ink, the ink receiving layer of the recording material is used. This is different from the so-called beading phenomenon that occurs when the amount of ink applied is excessive with respect to the ink absorptivity and the ink overflows.

  As a result of intensive studies on the phenomenon of microbeading that appears when a monochromatic image is formed using a light black ink, the present inventors have reduced the drying speed of the pigment on the recording material, It has been found that this phenomenon can be alleviated. However, by simply delaying the drying speed of the pigment on the recording material, the fixability after the ink is applied to the recording material is greatly deteriorated. In this case, the image quality may be deteriorated. Occur. Accordingly, the present inventors can provide a water-based ink that suppresses the microbeading phenomenon that occurs when an image is formed using the above-described light black ink and that does not cause deterioration of the fixing property of the ink. Recognized that it was a big challenge. In particular, obtaining the water-based ink as described above is a big problem for obtaining a good image by the ink jet recording method.

  Accordingly, an object of the present invention is to provide a water-based light containing a nonionic surfactant for improving penetrability and containing a small amount of carbon black in the ink when forming an image on glossy or semi-glossy paper. It is an object of the present invention to provide a water-based ink capable of suppressing microbeading phenomenon that occurs when a monochrome image is formed using black ink and realizing good fixing properties.

  Furthermore, another object of the present invention is to form an image that can realize image uniformity and further excellent fixability by using the water-based ink or the ink in combination with another water-based ink as a set for image formation. An ink jet recording method, an ink cartridge, an ink unit, and a recording apparatus are provided.

  The above object is achieved by the present invention described below. That is, the present invention comprises carbon black in an amount of 0.2 to 1.5% by mass and nonionic surfactant in an amount of 0.5 to 3.0% by mass. A water-soluble organic compound that is solid in a simple substance and a water-soluble organic compound that is liquid in a simple substance at 25 ° C. and has a surface tension value of 25 mN / m or more at 25 ° C. Water-soluble including at least one and having the total amount of the water-soluble organic compound in the ink in the range of 30 to 40% by mass and having a surface tension value at 25 ° C. of less than 35 mN / m. It is a water-based ink characterized by not containing an organic compound.

  Moreover, the following are mentioned as a preferable form of the said water-system ink. It is mentioned that the nonionic surfactant is an acetylene glycol surfactant, and that the water-soluble organic compound that is solid at 25 ° C. is not a saccharide. Furthermore, as a preferable form, the water-soluble organic compound that is solid in a simple manner at 25 ° C. is urea, thiourea, ethylene urea, trimethylolpropane, trimethylolethane, and polyethylene glycol having an average molecular weight of 1,000 or more. Can be mentioned.

  Another embodiment of the present invention comprises any one of the above-described water-based inks, cyan ink, magenta ink, yellow ink, black ink, red ink, green ink, blue ink, orange ink, and violet ink. A water-based ink set comprising a combination of at least one water-based ink selected from a group.

  Moreover, the following are mentioned as another embodiment of this invention. An inkjet recording method comprising at least a step of ejecting the aqueous ink according to any one of the above or each aqueous ink constituting the aqueous ink set by an inkjet recording method. An ink cartridge comprising the water-based ink according to any one of the above or each water-based ink constituting the water-based ink set. A water-based ink according to any one of the above or each water-based ink constituting the water-based ink set is individually stored, and an ink jet head for discharging the ink is provided. And recording unit. A water-based ink according to any one of the above or each water-based ink constituting the water-based ink set is individually stored, and an ink jet head for discharging the ink is provided. An inkjet recording apparatus. An image forming method, wherein an image is formed on a recording material using any one of the water-based inks described above or each water-based ink constituting the water-based ink set.

  As described above, according to the present invention, when forming an image using a light black ink having a relatively low carbon black content and containing a nonionic surfactant for improving permeability. There is provided an aqueous light black ink that can suppress the occurrence of the microbeading phenomenon and that can achieve good fixing properties. In addition, according to the present invention, by using the above-described light black ink, a water-based ink set capable of forming a high-quality image in which microbeading phenomenon is reduced and good fixability is realized, and the same A recording method, an ink cartridge, an ink unit, and a recording apparatus are provided.

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments of the present invention. As a result of intensive studies on the above-mentioned problems of the prior art, the present inventors have used light black ink having a low carbon black content in the ink for image formation by controlling the ink composition, particularly the water-soluble organic compound. Even in such a case, it is possible to control the existence form of the carbon black ink after being applied to the recording material, and thereby, two problems such as suppression of the micro beading phenomenon and suppression of deterioration of the fixing property of the ink. As a result, the present invention has been found.

  The present inventors consider the reason why the above-described excellent effect can be obtained by using the light black ink that is the water-based ink according to the present invention and the conventional problems can be solved as follows. Yes. First, when a single color image is formed on glossy or semi-glossy paper using light black ink with a low carbon black content in the ink, a micro beading phenomenon that occurs at low duty, which is a new problem unique to pigment inks, occurs. In particular, the cause of multipass recording will be considered.

  Here, multi-pass printing is the so-called multi-pass printing and divided printing scan times where the nozzle array of each color scans n times to form an image on the recording area of the recording material. According to this recording method, recording is performed while complementing each scan so that the recording duty per scan is reduced and the image is completed n times as the number of passes increases.

  FIG. 4A shows a state after the ink droplet of the first pass has landed on the cross section of the recording material 90. At this time, the components 92 other than the pigment in the ink penetrate into the recording material, but the carbon black pigment 91 is larger in size than the pores of the ink receiving layer formed on the surface of the recording material 90. It does not penetrate inside the recording material and exists on the surface of the recording material 90.

  At this time, the light black ink has a lower carbon black content in the ink than the black ink having a higher carbon black content in the ink. The number of carbon blacks 91 existing on the surface of the material 90 is also small (see FIG. 4A). In this aggregate of carbon blacks 91 with a small number of existence, since there are few water and solvent components in the periphery and inside of the recording material 90 where the carbon black 91 has landed, the ink droplets in the first pass of the light black ink are present. When it hits, it will dry quickly. On the other hand, in the case of an ink having a high carbon black 91 content, when the ink lands on the recording material 90, the carbon black 91 is overlapped and a large amount of water is present around or inside the carbon black 91. And solvent components, the drying speed is slower than when the light black ink is landed.

  As described above, in multi-pass printing, the light black ink with a low carbon black 91 content causes the ink droplets in the first pass to dry quickly, and the water droplets before the ink droplets 93 in the next second pass land. In addition, the surface of the recording material is dried by the permeation and diffusion of the ink solvent, so that the pores on the surface are blocked with carbon black pigment particles.

  Due to such a mechanism, when forming a multi-pass image using light black ink, there is a portion where a thin layer of carbon black 91 on the surface of the recording material 90 becomes as if it is “stop”. . For this reason, when ink drops thereafter land, the absorption of these inks is obstructed even though there is room for absorbing ink in the ink receiving layer of the recording material at a relatively low duty. It is considered that unevenness occurs between the part that is done and the part that is not.

  In addition, the ink component in the portion where the absorption is inhibited moves irregularly in the surface direction of the surface of the ink receiving layer of the recording material 90, and forms an aggregate of adjacent dots and new dots. As a result, as shown in FIG. 4 (b), these actions cause uneven distribution between a portion where the carbon black particles 91 are gathered on the surface of the recording material 90 and a portion where the carbon black particles 91 are not gathered. Fine density unevenness occurs. When multi-pass printing is performed using light black ink by the above process, as shown in FIG. 5, fine mottled density unevenness that can be confirmed with the naked eye appears in the formed image. That is, it is presumed that the micro beading phenomenon is caused by the fine mottled density unevenness and the image quality is deteriorated.

  The microbeading phenomenon as described above is particularly noticeable in penetrating inks in which high-speed fixability is emphasized and the surface tension of the ink is reduced using a surfactant, a penetrating organic solvent, or the like. This is because, in the penetrating ink as described above, the drying speed of the pigment is promoted by increasing the permeation speed of water and the organic solvent in the recording material inside direction, and the above-described pores on the surface of the recording material are removed. This is because the effect of “stopping” will increase.

  From the above, it is considered that the microbeading phenomenon can be suppressed by slowing the drying of the pigment on the recording material. Specific methods for slowing the drying of the pigment include reducing the content of the penetrant material in the ink and increasing the surface tension, and increasing the amount of the non-volatile solvent in the ink so that the ink is applied to the recording material. A method of slowing the evaporation of the solvent component in the vicinity of the pigment after landing and being applied can be considered. However, when the ink having the composition as described above is used, the microbeading phenomenon is surely suppressed, but the penetration of the water-based component in the recording material internal direction after the ink is applied to the recording material. Since it becomes slow, the color material is dried and the time required for fixing becomes longer, and the fixing property is impaired.

  Therefore, in order to achieve both suppression of the microbeading phenomenon and good fixability, the present inventors appropriately used as constituent components such as a water-soluble organic compound and a surfactant as a penetrant in the ink. The amount of pigment particles present immediately after the ink has landed on the recording material is controlled by optimizing the amount of the selected material, and as a result, the above object can be achieved. Invented.

  Here, a process from when the light black ink, which is a water-based ink according to the present invention, lands on a recording material and a monochromatic image is formed near the surface of the recording material will be described. FIG. 6A shows a state where an ink droplet of the first pass has landed on the cross section of the recording material 100. At this time, most of the aqueous component 102 other than the pigment in the ink quickly penetrates into the recording material. However, a water-soluble organic compound having a high surface tension of 35 mN / m or more, which can be a constituent component of the ink in the present invention, has a content in the ink of 30% to 40% by mass. Immediately after ink landing, there are many in the vicinity of the pigment without penetrating into the recording material.

  In addition, the water-soluble organic compound that is a solid at 25 ° C., which is a constituent component of the ink in the present invention, rapidly increases in viscosity due to water evaporation after landing of ink droplets. It tends to remain on the surface rather than the component, and immediately after ink landing, it exists in the vicinity of the pigment without penetrating the recording material. In particular, when the substance that is solid at room temperature is a substance having a function as a moisturizing agent, such as trimethylolpropane, the above phenomenon is caused more remarkably.

  Since the water-based ink according to the present invention contains the water-soluble organic compound having the above-described characteristics, when the ink lands on the recording material in the first pass, the carbon black pigment 101 is in the vicinity of the particle. In addition, since the ink component 103 mainly composed of a water-soluble organic compound that does not easily penetrate into these recording materials is retained, extreme drying until the ink droplet 104 in the second pass is landed is alleviated. For this reason, in the next printing pass, there is no portion where the ink absorption is hindered, so that the ink droplet 104 can penetrate evenly and uniformly. Therefore, as shown in FIG. 6B, the pigment particles can exist on the surface of the recording material without being evenly distributed. By the above process, the formed monochromatic image has a uniform image without the micro beading phenomenon as shown in FIG.

  The water-based ink according to the present invention having the above-described configuration is different from the case where the penetrability of the ink into the recording material is controlled by simply defining the amount of the surfactant contained in the ink. For example, it is possible to suppress the microbeading phenomenon by reducing the amount of the surfactant in the ink and slowing the penetration of the ink, but in this case, the fixability is extremely lowered. On the other hand, when the amount of the surfactant is increased, a microbeading phenomenon occurs even if good fixability is obtained.

  On the other hand, as a result of intensive studies by the present inventors, when designing an ink, a water-soluble organic compound having a low penetration rate into the recording material as described above and a nonion that functions as a penetrant The present inventors have found out that it is possible to achieve both suppression of the microbeading phenomenon and good fixability by defining and optimizing the content of the surfactant in the ink. Hereafter, each component which comprises the water-system ink concerning this invention is demonstrated.

<Carbon black content>
The water-based ink according to the present invention has a carbon black content of 0.2 to 1.5% by mass and is used as a light black ink. In the case of ink containing carbon black at a concentration higher than this, as described above, since a large amount of carbon black particles are present on the recording material when landed, the time required for drying increases. The microbeading phenomenon which is a problem of the invention is unlikely to occur. On the other hand, in order to obtain the effects of using light black ink for image formation, such as improved color reproducibility for dark colors such as shadows, improvement of gray gradation, and stability of gray balance, it is included in the ink. The carbon black content is preferably in the range of 0.2 to 1.5 mass%. The carbon black used in the present invention will be described later.

<Content of water-soluble organic compound with slow penetration rate>
Furthermore, the present inventors have described above in order to achieve both suppression of the microbeading phenomenon and good fixability in an ink having a low carbon black content of 0.2 to 1.5% by mass. Detailed investigations were made on the incorporation of a water-soluble organic compound having a low penetration rate into the recording material into the ink. As a result, the ink contains a water-soluble organic compound that is solid at 25 ° C. or a water-soluble organic compound that is liquid at 25 ° C. and has a surface tension value of at least 35 mN / m at 25 ° C. The effect of the present invention is most exerted when the total amount of these water-soluble organic compounds is in the range of 30 to 40% by mass, and the microbeading phenomenon. It was found that both the suppression of the toner and the good fixing property can be achieved at a high level. In addition, the specific example of the said water-soluble organic compound used by this invention is mentioned later.

  As the water-soluble organic compound to be contained in the ink, other than the above, a water-soluble organic compound that is liquid at 25 ° C. but has a surface tension at 25 ° C. of less than 35 mN / m, that is, a penetrating solvent is present in the ink. In this case, when ink suitability is reached, the penetration of components other than the pigment, such as water and water-soluble organic compounds, into the recording material becomes too high, and the drying of the pigment is promoted. The deterioration of image quality becomes remarkable, which is not preferable.

  Even when the total amount of the water-soluble organic compound used in the present invention in the ink is less than 30% by mass, the microbeading phenomenon is likely to occur because the pigment is quickly dried. On the other hand, when the total amount of the water-soluble organic compound used in the present invention in the ink is more than 40% by mass, good fixability cannot be obtained. When used, it is not preferable because it is liable to cause problems such as defective ink ejection.

<Content of nonionic surfactant>
The water-based ink according to the present invention contains a nonionic surfactant in the range of 0.5 to 3.0% by mass, and includes a nonionic surfactant having an ethylene oxide group, in particular, an acetylene glycol surfactant. It is preferable to use it. When the content of the nonionic surfactant is less than 0.5% by mass, good fixability cannot be obtained, and when the content is more than 3.0% by mass, particularly when it is used for inkjet recording or the like. In addition, the ink discharge performance from the resting state is adversely affected.

[Nonionic surfactant]
Examples of the nonionic surfactant having an ethylene oxide group include compounds having the structures of the following structural formulas (1) to (4).

(In the structural formula (1), R represents alkyl and n represents an integer.)

  In the structural formula (1), R is preferably an alkyl having 8 to 21 carbon atoms. R may be linear or branched. n is preferably an integer of 5 to 40. It is also possible to use a mixture of two or more compounds having different values of R and / or n.

(In the structural formula (2), R represents an alkyl group, and n represents an integer.)

  In the structural formula (2), R is preferably an alkyl having 8 to 21 carbon atoms. R may be linear or branched. n is preferably an integer of 5 to 40. It is also possible to use a mixture of two or more compounds having different values of R and / or n.

(In the structural formula (3), R represents a hydrogen atom or an alkyl group, and m and n each represents an integer.)

  In the structural formula (3), m is preferably an integer of 1 to 10. n is preferably an integer of 1 to 10. In addition, m means the number of ethylene oxide units, n means the number of propylene oxide units, and any of a block copolymer, an alternating copolymer, and a random copolymer may be used. A mixture of two or more compounds having different values of m and / or n can also be used.

(In the structural formula (4), m and n each represents an integer.)

  In the structural formula (4), m is preferably an integer of 1 to 10. n is preferably an integer of 1 to 10. A mixture of two or more compounds having different values of m and / or n can also be used.

  When the nonionic surfactant having an ethylene oxide group of the structural formulas (1) to (4) listed above is used in a specific amount, the effect of the present invention can be sufficiently obtained, but above all, the above structural formula (4) When an acetylene glycol surfactant represented by the formula (1) is used, it is most preferable because a particularly excellent effect is obtained in fixability. Furthermore, the value of m + n in the structural formula (4) is particularly preferably 3 or more. When the value of m + n is less than 3, it is not preferable because the hydrophobicity is large and the solubility in water-based ink is low and separation is likely to occur in the ink.

[Water-soluble organic compounds]
The water-based ink according to the present invention comprises a mixed medium of a water-soluble organic medium and water as a carbon black dispersion medium. For the reasons described above, the water-based ink is a water-soluble organic medium that is solid as a single substance at 25 ° C. Either a water-soluble organic compound or a water-soluble organic compound that is liquid alone at 25 ° C. and has a surface tension value of at least 35 mN / m at 25 ° C. It needs to be a thing. Further, the total amount of the water-soluble organic compound is required to be in the range of 30 to 40% by mass. However, the water-based ink does not contain a water-soluble organic compound having a surface tension value alone at 25 ° C. smaller than 35 mN / m.

  Examples of water-soluble organic compounds that are solid at 25 ° C. include urea and derivatives thereof, moisturizing solids such as trimethylolpropane and trimethylolethane, saccharides and derivatives thereof, and polyethylene glycol having an average molecular weight of 1,000 or more. Can be mentioned. These are preferably in the range of 0.1 to 20.0% by mass with respect to the ink, and more preferably in the range of 3.0 to 10.0% by mass.

  However, when a saccharide is used as a water-soluble substance that is solid at 25 ° C. alone, although it can solve the microbeading phenomenon, it may cause another problem, so it is not preferable. That is, when the ink according to the present invention is used in an ink jet printer, when the printer is left unused for a certain period of time, or when the ink tank and the print head are integrated, the print head itself is removed from the printer. If the ink tank and the print head are separable from the printer, or if the ink tank is left detached from the printer, moisture evaporation will occur in the ink at the nozzle tip. In some cases, the fixing of the coloring material and the solid component of the material relatively increases and is fixed, so that clogging occurs, so-called deterioration of fixing property is observed.

  On the other hand, trimethylolpropane, trimethylolethane, or polyethylene glycol having an average molecular weight of 1,000 or more rarely impairs reliability such as stickiness even when contained in a relatively large amount in the ink. Therefore, the water-soluble organic compound that is solid at 25 ° C. constituting the water-based ink according to the present invention is a compound having excellent moisture retention, such as trimethylolpropane, trimethylolethane, or polyethylene glycol having an average molecular weight of 1,000 or more. It is particularly preferred to use

  When a water-soluble organic compound that is a single liquid at 25 ° C. is selected and used as the water-soluble organic compound constituting the water-based ink according to the present invention, the surface tension value at 25 ° C. alone is 25. When a compound having a temperature of 35 mN / m or more is selected at 25 ° C. and used in combination with a water-soluble organic compound that is solid at 25 ° C. or when a plurality of the above-described organic compounds are used, these water-soluble organic compounds are used. It is necessary to prepare an ink by selecting a water-soluble organic compound and mixing it appropriately so that the total amount of the compound falls within the range specified in the present invention.

  The water-soluble organic solvent used in the water-based ink according to the present invention is not limited as long as the above conditions are satisfied. For example, alkyl alcohols; amides; ketones or keto alcohols; ethers such as tetrahydrofuran and dioxane; Alkylene glycols; alkylene glycols; polyhydric alcohols such as glycerin; N-methyl-2-pyrrolidone, 2-pyrrolidone and the like can be used.

  Further, it is desirable to use deionized water as the water used in the water-based ink according to the present invention. The amount of water contained in the ink is preferably in the range of 40 to 70% by mass with respect to the total mass of the ink.

[Carbon black]
As described above, the water-based ink according to the present invention is used as a light black ink, and contains 0.2 to 1.5% by mass of carbon black pigment in the ink. As the carbon black used in the present invention, for example, carbon black produced by a known method such as a contact method, a furnace method, or a thermal method can be used.

  Specifically, for example, Raven 7000, Ray Van 5750, Ray Van 5250, Ray Van 5000 ULTRA, Ray Van 3500, Ray Van 2000, Ray Van 1500, Ray Van 1250, Ray Van 1200, Ray Van 1190 ULTRA-II, Ray Van 1170, Ray Van 1255 (above, Colombia), Black Pearls L, Legal 400R, Legal 330R, Legal 660R, Mogul L, Monarch 700, Monak 800, Monak 880, Monak 900, Monak 1000, Monak 1100, Monak 1300, Monak 1400, Monak 2000, Valcan XC-72R (above, Bot), Color Black FW1, Color Black FW2, Color Black FW2V, Color Black FW18, Color Black FW200, Color Black S150, Color Black S160, Color Black S170, Printex 35, Printex U, Printex V, Printex 140U, Printex 140V, Special Black 6, Special Black 5, Special Black 4A, Special Black 4 (above, manufactured by Degussa), No. 25, no. 33, no. 40, no. 47, no. 52, no. 900, no. Commercial products such as 2300, MCF-88, MA600, MA7, MA8, MA100 (above, manufactured by Mitsubishi Chemical Corporation) can be used. Carbon black newly prepared for the present invention can also be used. However, the present invention is not limited to these, and any conventionally known carbon black can be used.

  In the present invention, the above-described carbon black is preferably added to the ink as a pigment dispersion obtained by dispersing it in an aqueous medium with a dispersant or the like.

  As the pigment dispersion used in this case, carbon black whose surface is modified by using a surfactant as a dispersant or introducing a hydrophilic group contributing to dispersion to the surface of the carbon black particles is used. Although what is obtained by the method to disperse | distribute is mentioned, It is preferable that it is what was resin-dispersed or / and microencapsulated. That is, by using a pigment dispersion containing a resin, it is possible to achieve both uniform gloss and a sufficient image density when an image is formed on glossy paper. Such an effect is considered to be obtained by the relationship between the concentration of carbon black in the ink and the resin component as a dispersant contributing to dispersion, the resin component used when microencapsulated, and the like.

  The pigment dispersion that can be suitably used in the present invention will be described. First, a pigment dispersion obtained by dispersing carbon black using a resin dispersant will be described. As the resin dispersant used at this time, natural polymers can also be used, but more preferred examples include synthetic polymers, and more specifically, water-soluble polymer compounds. A method for producing a water-soluble polymer compound that can be used as a resin dispersant is not particularly limited. For example, a monomer having an ionic group and another polymerizable monomer can be used in the presence of a catalyst in a non-reactive solvent. It can manufacture by making it react under or absence.

  More specific resin dispersants include, for example, styrene and its derivatives, vinyl naphthalene and its derivatives, aliphatic alcohol esters of α, β-ethylenically unsaturated carboxylic acids, acrylic acid and its derivatives, maleic acid and its At least two monomers selected from derivatives, itaconic acid and derivatives thereof, fumaric acid and derivatives thereof, vinyl acetate, vinyl alcohol, vinylpyrrolidone, acrylamide and derivatives thereof (of which at least one is a hydrophilic monomer) Block copolymer, random copolymer, graft copolymer, and salts thereof. Here, as a preferred example, a styrene / acrylic polymer compound obtained by polymerizing a monomer having an ionic group and a styrene monomer as essential components, or a monomer having an ionic group, and a carbon atom Examples thereof include resin dispersants selected from ionic group-containing acrylic polymer compounds obtained by polymerizing 5 or more (meth) acrylic acid ester monomers as essential components. Although it has been clarified that good results are obtained when these resin dispersants are used, the present invention is not limited thereto.

  When carbon black is dispersed with the resin dispersant as described above, the anionic dispersant is used as the pigment obtained when the obtained pigment dispersion has an anionic group in particular. In particular, when the dispersion is intended to have a cationic group, it is desirable to select either a cationic group or a nonionic dispersant.

  Examples of the dispersion method of the carbon black pigment that can be used in the present invention include a disperser such as a paint shaker, a sand mill, an agitator mill, and a three roll mill, a high-pressure homogenizer such as a microfluidizer, a nanomizer, and an optimizer, and an ultrasonic wave. Any method is not limited as long as it is a dispersion method generally used for each color material, such as a disperser.

  Further, in the present invention, a pigment having a microcapsule structure that can be dispersed without using a dispersant or the like by increasing the dispersibility of the carbon black itself is also preferably used. Examples of the method for coating carbon black with organic polymers and microencapsulating include a chemical manufacturing method, a physical manufacturing method, a physicochemical method, and a mechanical manufacturing method. Specifically, interfacial polymerization method, in-situ polymerization method, submerged cured coating method, coacervation (phase separation) method, submerged drying method, melt dispersion cooling method, air suspension coating method, spray drying method , Acid precipitation method, phase inversion emulsification method and the like.

  Examples of organic polymers used as the material constituting the wall membrane material of the microcapsule include polyamide, polyurethane, polyester, polyurea, epoxy resin, polycarbonate, urea resin, melamine resin, phenol resin, polysaccharide, gelatin, Gum arabic, dextran, casein, protein, natural rubber, carboxypolymethylene, polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl acetate, polyvinyl chloride, polyvinylidene chloride, cellulose, ethyl cellulose, methyl cellulose, nitrocellulose, hydroxyethyl cellulose, cellulose acetate, polyethylene , Polystyrene, (meth) acrylic acid polymer or copolymer, (meth) acrylic acid ester polymer or copolymer, (meth) acrylic acid- (meth) Acrylic acid ester copolymer, styrene - (meth) acrylic acid copolymer, styrene - maleic acid copolymer, sodium alginate, fatty acids, paraffin, beeswax, water wax, hardened beef tallow, carnauba wax, albumin and the like.

  Among these, organic polymers having an anionic group such as a carboxylic acid group or a sulfonic acid group can be used. Nonionic organic polymers include, for example, polyvinyl alcohol, polyethylene glycol monomethacrylate, polypropylene glycol monomethacrylate, methoxypolyethylene glycol monomethacrylate, or their (co) polymers, and 2-oxazoline cationic ring-opening polymers. Etc. In particular, a complete saponified product of polyvinyl alcohol is particularly preferable because it has low water solubility and is easily dissolved in hot water but difficult to dissolve in cold water.

  When the phase inversion method or the acid precipitation method is selected as the microencapsulation method, anionic organic polymers are used as the organic polymers constituting the wall membrane material of the microcapsules. The phase inversion method is a composite of an anionic organic polymer having self-dispersibility or solubility in water and a dispersible pigment, or a composite, or a dispersible pigment, curing A mixture of an agent and an anionic organic polymer is used as an organic solvent phase, and water is added to the organic solvent phase, or the organic solvent phase is added to water to achieve self-dispersion (phase inversion emulsification). This is a microencapsulation method. In the above phase inversion method, there is no problem even if the organic solvent phase is produced by mixing a water-soluble organic solvent or additive used in the ink. In particular, it is more preferable to mix an ink liquid medium because a dispersion liquid for ink can be directly produced.

  On the other hand, in the acid precipitation method, a part or all of the anionic groups of the anionic group-containing organic polymers are neutralized with a basic compound, and a dispersible pigment is kneaded in an aqueous medium and acidic. A hydrous cake obtained by a process comprising a step of precipitating an anionic group-containing organic polymer by neutralizing or acidifying the compound with a compound and fixing it to a pigment is obtained by using a basic compound to form an anionic group. It is a method of microencapsulation by neutralizing a part or all of it. By doing in this way, the anionic microencapsulated pigment which is fine and contains many pigments can be manufactured.

  Examples of the solvent used for microencapsulation as described above include alkyl alcohols such as methanol, ethanol, propanol and butanol; aromatic hydrocarbons such as benzol, toluol and xylol; methyl acetate Esters such as ethyl acetate and butyl acetate; Chlorinated hydrocarbons such as chloroform and ethylene dichloride; Ketones such as acetone and methyl isobutyl ketone; Ethers such as tetrahydrofuran and dioxane; Cellosolves such as methyl cellosolve and butyl cellosolve Etc. The microcapsules prepared by the above method are separated once from these solvents by centrifugation or filtration, and then stirred and redispersed with water and the necessary solvent to obtain the desired microcapsule type pigment. It can also be.

  Further, as the pigment dispersion used in the present invention, a dispersion of a polymer-bonded self-dispersing pigment that is dispersible without using a dispersant or the like, in which the dispersibility of carbon black itself is enhanced, can also be used. This polymer-bonded self-dispersing pigment that does not use a dispersant is a combination of a functional group that is chemically bonded to the surface of carbon black, either directly or via another atomic group, and an ionic monomer and a hydrophobic monomer. It is preferable to use one containing a reaction product with a polymer. That is, if a material having such a structure is used, the copolymerization ratio between the ionic monomer and the hydrophobic monomer, which is a material for forming a copolymer used for modifying the surface, can be appropriately changed. This is preferable because the hydrophilicity of the carbon black modified thereby can be appropriately adjusted. Moreover, since the kind of ionic monomer and hydrophobic monomer to be used, and a combination of both can be appropriately changed, various characteristics can be imparted to the carbon black surface, which is also preferable from this point.

  The particle size obtained in the process of making carbon black into a pigment dispersion by the above-described method is preferably in the range of 0.01 to 0.5 μm (10 to 500 nm), particularly preferably 0. Disperse in a range of 0.03 μm to 0.3 μm (30 nm to 300 nm). The dispersed particle size in this process greatly affects the dispersed particle size of the resulting dispersible pigment. From the viewpoints of coloring power, weather resistance of the image, and dispersion stability, the above range is preferable.

[Other ingredients]
In the water-based ink according to the present invention, in addition to the above components, if necessary, surfactants other than those described above, pH adjusters, rust inhibitors, preservatives, antifungal agents, antioxidants, reduction inhibitors, Various additives such as an evaporation accelerator and a chelating agent may be contained.

  That is, as a surfactant, in addition to the nonionic surfactant having an ethylene oxide group, which is essential in the present invention, for example, in combination with these, in order to improve the surface tension adjustment and ejection properties Other surfactants may be used. The total content of the additives as described above in the aqueous ink is preferably in the range of 0.05 to 5% by mass with respect to the total mass of the aqueous ink. More preferably, it is 0.1-2 mass%.

[Ink characteristics]
The water-based ink according to the present invention comprising the constituent components as described above is particularly suitable for inkjet recording. In such a case, it is preferable that the ink has a characteristic that can be satisfactorily discharged from the ink jet recording head. For this reason, from the viewpoint of ejectability from the ink jet recording head, the ink characteristics are, for example, a viscosity of 1 to 15 mPa · s, a surface tension of 25 mN / m or more, and a viscosity of 1 to 5 mPa · s. The surface tension is preferably 25 to 50 mN / m.

  That is, when the viscosity of the ink is within the above range, normal ejection is possible in ink jet recording, and the penetration into the recording material is quick due to the viscosity resistance, and there is no problem in terms of fixability. . When the surface tension is in the above range, after droplets are ejected in ink jet recording, the force to pull back the meniscus is strong, or conversely, when the meniscus protrudes, the force to pull back is relatively strong, so The problem that the orifice portion gets wet and causes the twisting of the orifice portion does not occur.

[Ink set]
The aqueous ink according to the present invention is a combination of at least one aqueous ink selected from the group consisting of cyan ink, magenta ink, yellow ink, black ink, red ink, green ink, blue ink, orange ink, and violet ink. The water-based ink set is particularly preferably used for ink jet recording.

  Specifically, a light black ink having a relatively low carbon black density, which is a water-based ink according to the present invention, for example, a black ink having a relatively high carbon black density, further cyan ink, magenta ink, yellow ink, Examples include those obtained by combining color inks selected from various possible color inks such as red ink, green ink, blue ink, orange ink, and violet ink.

  The ink set according to the present invention includes a combination of the above-described ink tanks that individually store inks, and an ink tank that is an integral combination of ink tanks that individually store several inks. Or an ink set composed of an ink tank with a head, or an ink set configured such that individual ink tanks can be attached to and detached from the recording apparatus. In the present invention, a state where a plurality of inks are used by combining other inks with the water-based ink according to the present invention is substantially referred to as an ink set. In any case, in the present invention, the water-based ink according to the present invention is combined without being limited to other inks (in a printer or as an ink tank) that are used when the ink set according to the present invention is used. As long as it is made, it is not limited to the above-described form, and any modification form may be used.

[Recording method and recording apparatus]
The water-based ink according to the present invention is particularly effective when an image is formed on a recording material by an ink jet recording apparatus as will be described later. Any recording material that can be used for ink jet recording can be used without limitation.

  The water-based ink according to the present invention is suitably used for an inkjet discharge type head, and is also effective as an ink tank in which the ink is stored or as a filling ink. In particular, the water-based ink according to the present invention provides an excellent effect when used in a bubble jet (registered trademark) type recording head, recording unit, or recording apparatus among ink jet recording methods.

  The typical configuration and principle of the ink jet ejection method are performed using the basic principle disclosed in, for example, US Pat. Nos. 4,723,129 and 4,740,796. Those are preferred. This method is applicable to both so-called on-demand type and continuous type. In particular, in the case of the on-demand type, the electrothermal transducer disposed corresponding to the sheet or liquid path holding the ink is subjected to a rapid temperature rise corresponding to the recorded information and exceeding the nucleate boiling. By applying at least one drive signal, heat energy is generated in the electrothermal transducer and the film is boiled on the heat acting surface of the recording head, resulting in a one-to-one correspondence to this drive signal and bubbles in the ink. Is effective. By the growth and contraction of the bubbles, ink is ejected through the ejection opening to form at least one ink droplet. It is more preferable that the drive signal has a pulse shape, because the bubble growth and contraction is performed immediately and appropriately, and thus ink discharge with particularly excellent responsiveness can be achieved. As this pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. Further excellent recording can be performed by employing the conditions described in US Pat. No. 4,313,124 of the invention relating to the temperature rise rate of the heat acting surface.

  As the configuration of the recording head, in addition to the combination configuration (straight liquid flow path or right-angle liquid flow path) of the discharge port, the liquid path, and the electrothermal transducer as disclosed in each of the above-mentioned specifications, the thermal action As an ink for use in an ink jet ejection system having a configuration using US Pat. No. 4,558,333 and US Pat. No. 4,459,600 which disclose a configuration in which a portion is disposed in a bent region However, the water-based ink according to the present invention is effective. In addition, if it is common to a plurality of electrothermal transducers, it is also effective for a configuration in which the ejection holes are used as ejection portions of the electrothermal transducer (Japanese Patent Laid-Open No. 59-123670, etc.). Furthermore, as a full-line type recording head having a length corresponding to the width of the maximum recording material that can be recorded by the recording apparatus, the length of the recording head is determined by a combination of a plurality of recording heads as disclosed in the above specification. Any of a configuration satisfying the above and a configuration as a single recording head formed integrally may be used, but the present invention can exhibit the above-described effects more effectively.

  In addition, it is mounted on the main body of the device so that it can be electrically connected to the main body of the device and supplied with ink from the main body of the device. The present invention is also effective when a cartridge type recording head is used. Specifically, FIG. 1 is a diagram illustrating an example of an ink cartridge 45 that stores ink supplied to a recording head via an ink supply member, for example, a tube. Reference numeral 40 denotes an ink container, for example, an ink bag, which stores ink for supply, and a rubber plug 42 is provided at the tip of the ink container. By inserting a needle (not shown) into the stopper 42, the ink in the ink bag 40 can be supplied to the head. Reference numeral 44 denotes an ink absorber that receives waste ink. The ink container preferably has a liquid contact surface made of polyolefin, particularly polyethylene. The ink cartridge may have a configuration in which an ink storage portion and a head portion are integrated.

(ink cartridge)
Examples of the ink cartridge suitable for performing recording using the water-based ink according to the present invention include an ink cartridge having an ink storage portion for storing these inks.

  Specific examples of ink cartridges suitable for recording using the water-based ink of the present invention are shown below. FIG. 2 is a schematic explanatory view and a sectional view of a liquid storage container which is an ink cartridge suitable for recording using the water-based ink of the present invention. As shown in FIG. 2, the liquid storage container (ink tank) communicates with the atmosphere through the atmosphere communication port 112 at the upper part and communicates with the ink supply port at the lower part. A partition wall 138 partitions the negative pressure generating member storage chamber 134 for storing the member and a substantially sealed liquid storage chamber 136 for storing the liquid ink. The negative pressure generating member storage chamber 134 and the liquid storage chamber 136 are close to the bottom of the liquid storage container (ink tank), and the communication hole 140 formed in the partition wall 138 and the air supply to the liquid storage chamber during the liquid supply operation. It communicates only through an air introduction groove (atmosphere introduction path) 150 for promoting introduction. A plurality of ribs are integrally formed on the upper wall of the liquid container (ink tank) that defines the negative pressure generating member storage chamber 134 so as to protrude into the inside, and is compressed into the negative pressure generating member storage chamber 134. Is in contact with the negative pressure generating member accommodated in. By this rib, an air buffer chamber is formed between the upper wall and the upper surface of the negative pressure generating member.

  Further, the ink supply cylinder provided with the liquid supply port 114 is provided with a pressure contact body 146 having a higher capillary force and a higher physical strength than the negative pressure generating member, and is in pressure contact with the negative pressure generating member. In the illustrated example, two capillaries of a first negative pressure generating member 132B made of an olefin resin fiber such as polyethylene and a second negative pressure generating member 132A are used as the negative pressure generating member in the negative pressure generating member storage chamber. A force generating negative pressure generating member is accommodated. 132C is a boundary layer of the two negative pressure generating members, and an intersection portion of the boundary layer 132C with the partition wall 138 is an air introduction groove (atmosphere introduction) in a posture when the liquid storage container is used with the communication portion downward. Road) is present above the upper end of 150. Further, the ink accommodated in the negative pressure generating member exists above the boundary layer 132C as indicated by the ink level L.

(Recording unit)
The recording unit according to the present invention ejects the ink containing the water-based ink according to the present invention or an ink that constitutes an ink set formed by combining a plurality of inks including the ink, and the ink. And an inkjet head. The recording unit is not limited to one in which the head and the ink cartridge are separated as described above, but is preferably used for a unit in which they are integrated as shown in FIG. In FIG. 3, reference numeral 70 denotes a recording unit, in which an ink storage portion that stores ink, for example, an ink absorber, is stored. It is configured to be ejected as ink droplets. It is preferable to use polyurethane or polypropylene as the material of the ink absorber. Alternatively, a structure in which the ink container is an ink bag in which a spring or the like is prepared may be used without using the ink absorber. Reference numeral 72 denotes an atmosphere communication port for communicating the inside of the cartridge with the atmosphere.

  In the present invention, it is preferable to add recovery means for the recording head, preliminary auxiliary means, etc. provided as the configuration of the recording apparatus to be applied, because the effects of the present invention can be further stabilized. . Specifically, capping means for the recording head, cleaning means, pressurization or suction means, electrothermal converter or preheating means using a heating element different from these, or a combination thereof, and recording This is a preliminary discharge mode in which another discharge is performed.

[Recording material]
In the image forming method characterized by using the water-based ink or ink set according to the present invention, the recording material to be used is of course not limited, but it is at least one of various substrates such as paper and resin film. A recording material having a coating layer for receiving ink on the surface can be preferably used. In particular, a preferable effect is obtained when a recording material having a coating layer on the surface and using glossy paper or semi-glossy paper configured to exhibit glossiness. Examples of such a recording material include a recording material having a coating layer that receives ink on at least one surface containing at least a hydrophilic polymer and / or an inorganic porous material. When an image is formed, A particularly excellent effect is exhibited.

  As a recording material having a coating layer that receives ink, the surface state, the thickness of the coating layer, the size of pores that absorb ink, the difference in the material constituting the ink absorption layer, and the type of substrate, etc. There are a wide variety of things and a desired one may be used. For example, glossy paper or glossy film having a high surface gloss, fine glossy paper or semi-glossy paper whose surface gloss is adjusted by processing or the like can be used. In the present invention, among the above-mentioned recording materials, glossy paper with sufficient gloss, semi-glossy paper with a surface treated with silk, etc. can be suitably used.

  A conventionally known substance can be used as the hydrophilic polymer constituting the ink receiving layer of the recording material. For example, starch, carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, alginic acid, gelatin, polyvinyl alcohol, polyvinyl acetal, polyethylene oxide, sodium polyacrylate, cross-linked polyacrylic acid, polyvinyl methyl ether, polystyrene sulfonic acid, quaternary Examples thereof include polyvinyl pyridine, polyacrylamide, polyvinyl pyrrolidone, polyamine, aqueous urethane resin, water-soluble acrylic resin, water-soluble epoxy compound, and water-soluble polyester. In addition, modified products of the above polymers, for example, ion-modified products such as cation-modified polyvinyl alcohol and cation-modified polyvinyl pyrrolidone can be used as appropriate. Furthermore, examples of the inorganic porous material used for constituting the ink receiving layer of the recording material include silica gel, alumina, zeolite, and porous glass.

  As the glossy paper or semi-glossy paper used in the present invention, those having sufficient ink absorption speed and absorption capacity are preferably used. That is, in order to obtain a desired glossiness on the surface of the recording material and to obtain sufficient ink absorption ability, a recording material that is fine and has a sufficient ink-receiving layer thickness to absorb ink is suitable. It is. As such a recording material, the pore radius is generally 10 to 50 nm, for example, and preferably 20 nm or less. The thickness of the ink receiving layer is preferably 10 μm or more and 40 μm. Since the pore radius shown here, that is, the size of the pores of the recording material is smaller than that of the carbon black used in the present invention, the solvent component in the ink penetrates through the pores. Will remain on the surface and will be arranged.

  Next, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited by the following Example, unless the summary is exceeded. In the text, “parts” and “%” are based on mass unless otherwise specified.

[Preparation of carbon black dispersion]
A 10% sodium hydroxide neutralized aqueous solution of 10 parts of carbon black having a specific surface area of 210 m ² / g and a DBP oil absorption of 74 ml / 100 g, and a styrene-acrylic acid copolymer having an acid value of 200 and a weight average molecular weight of 10,000. 20 parts and further 70 parts of ion-exchanged water were mixed and dispersed for 3 hours using a batch type vertical sand mill. Thereafter, coarse particles were removed by centrifugation, and further filtered under pressure through a microfilter (manufactured by Fuji Film) having a pore size of 3.0 μm to obtain a black pigment dispersion having a carbon black concentration of 10%.

[Water-soluble organic compounds]
Next, with respect to each water-soluble organic compound used in Examples and Comparative Examples, the existence form of a simple substance at 25 ° C. and the surface tension at 25 ° C. of a simple substance was measured for those which were liquid. . The results are shown in Table 1. For measuring the surface tension, an automatic surface tension measuring device [trade name: CPVP-Z; manufactured by Kyowa Interface Chemical Co., Ltd.] was used.

[Examples 1-15, Comparative Examples 1-6]
Using the carbon black dispersion prepared above and the components selected from the water-soluble organic compounds listed in Table 1, each component was weighed to have the composition described in Table 2 or Table 3 containing these, The ingredients were fully dissolved and allowed to stir. Then, it pressure-filtered with the micro filter (product made from Fuji Film) with a pore size of 3.0 micrometers, and prepared each light black ink of Examples 1-15 and Comparative Examples 1-6. The values in Table 2 indicate the number of parts of each component, and the remainder means that the whole is adjusted to 100 parts with pure water. Since the carbon black concentration in the carbon black dispersion is 10% by mass, the carbon black content in the ink is 1/10 of the carbon black dispersion.

[Evaluation]
Using the light black inks of these examples and comparative examples, single color images were formed and evaluated. The evaluation was performed by forming an image using an inkjet recording apparatus BJF-900 having an on-demand type multi-recording head that ejects ink by applying thermal energy to the ink in accordance with a recording signal.

(Occurrence of micro beading phenomenon)
Using the above light black inks and the above-described ink jet recording apparatus, a monochrome image pattern having a driving amount of 100% was printed on Canon ink-jet paper SG-101. Then, the presence or absence of the occurrence of microbeading phenomenon in each formed image was visually observed and evaluated according to the following criteria. The evaluation results are summarized in Table 4.

AA: The microbeading phenomenon cannot be confirmed even when visually observed or magnified 10 times, and the formed image is uniform.
A: The microbeading phenomenon cannot be confirmed by visual observation, but is a level that can be visually recognized when it is magnified 10 times, and the formed image is at a level with no problem in image performance.
B: Fine color unevenness of the image due to the micro beading phenomenon can be visually recognized.
C: The occurrence of the micro beading phenomenon is conspicuous even visually, the formed image is non-uniform and the color unevenness is conspicuous.

(Fixability)
Using the above light black inks and the above-described ink jet recording apparatus, a monochrome image pattern having a driving amount of 100% was printed on Canon ink jet paper SG-101. Then, 10 seconds after printing, the printed part was rubbed with a filter paper (trade name: No. 5C; manufactured by Toyo Roshi Kaisha, Ltd.), and the appearance of the printed matter thereafter was visually observed to evaluate the fixability. Evaluation was performed according to the following criteria. The evaluation results are summarized in Table 4.

A: No smudges or tails are observed on the printed part.
B: Although a slight change occurs in the surface state of the print portion, it is a level at which there is no problem in image performance, and no tailing is observed.
C: Dirt and tailing of the printed part occurs.

(Fixability)
Using each of the light black inks of Example 1 and Example 15 and the above-described ink jet recording apparatus, a tank containing the light black ink was attached to the recording head, and the recording head was removed from the main body. It was left for 2 weeks in an environment of 15 ° C. and humidity. Thereafter, the recording head was attached to the above-mentioned recording apparatus, printing was performed, and ink stickiness was evaluated according to the following criteria. The evaluation results are shown in Table 5.

A: All the nozzles ejected normally within 3 suction recovery operations.
B: In the suction recovery operation 3 to 5 times, all nozzles ejected normally.
C: Within 5 suction recovery operations, all nozzles did not discharge normally, and ink ejection failure due to nozzle clogging and flying deviation were observed.

It is a longitudinal cross-sectional view of an ink cartridge. 3 is a schematic illustration of a liquid container that is an ink cartridge suitable for performing recording using the ink of the present invention. It is a perspective view which shows an example of a recording unit. It is a figure for demonstrating typically a mode observed from the cross section, when light black ink lands on a recording material and a micro beading phenomenon occurs. 5 is an image formed by the process of FIG. It is a figure for demonstrating typically a mode that it observed from the cross section when the ink droplet of this invention landed on a recording material. FIG. 7 is a monochrome image formed by the process of FIG. 6. FIG.

Explanation of symbols

40: Ink bag 42: Plug 44: Ink absorber 45: Ink cartridge 70: Recording unit 71: Head unit 72: Air communication port 90: Recording material 91: Carbon black pigment 92: Aqueous system other than carbon black pigment in ink Component 93: Ink droplet 100: Recording material 101: Carbon black pigment 102: Aqueous component mainly containing water 103: Aqueous component mainly containing a water-soluble organic compound used in the present invention 104: Ink droplet 112: Atmosphere Communication port 114: liquid supply port 132A: second negative pressure generating member 132B: first negative pressure generating member 132C: boundary layer 134 between the first negative pressure generating member and the second negative pressure generating member: negative pressure generation Member storage chamber 136: Liquid storage chamber 138: Partition wall 140: Communication hole 146: Press contact body 150: Atmosphere introduction groove (atmosphere introduction path)
L: Liquid-gas interface

Claims (10)

  A water-soluble organic compound comprising carbon black in an amount of 0.2 to 1.5% by mass and nonionic surfactant in an amount of 0.5 to 3.0% by mass; And at least one of a water-soluble organic compound that is liquid at 25 ° C. and has a surface tension value of at least 35 mN / m at 25 ° C., and that contains the water-soluble organic compound in the ink. A water-based ink characterized by not containing a water-soluble organic compound whose total amount is in the range of 30 to 40% by mass and whose surface tension value at 25 ° C. is smaller than 35 mN / m.   The water-based ink according to claim 1, wherein the nonionic surfactant is an acetylene glycol surfactant.   The water-based ink according to claim 1, wherein the water-soluble organic compound that is solid at 25 ° C. is not a saccharide.   2. The water-soluble organic compound that is solid at 25 ° C. is selected from the group consisting of urea, thiourea, ethylene urea, trimethylolpropane, trimethylolethane, and polyethylene glycol having an average molecular weight of 1,000 or more. The water-based ink according to any one of -3.   The water-based ink according to any one of claims 1 to 4, and selected from the group consisting of cyan ink, magenta ink, yellow ink, black ink, red ink, green ink, blue ink, orange ink, and violet ink. A water-based ink set comprising a combination of at least one water-based ink.   An ink jet recording method comprising at least a step of discharging the water based ink according to any one of claims 1 to 4 or each water based ink constituting the ink set according to claim 5 by an ink jet recording method. .   An ink cartridge comprising: the water-based ink according to any one of claims 1 to 4; or each water-based ink constituting the ink set according to claim 5.   An ink storage unit in which each of the water-based inks according to any one of claims 1 to 4 or each water-based ink constituting the ink set according to claim 5 is individually stored, and for discharging the ink A recording unit comprising an inkjet head.   An ink storage unit in which each of the water-based inks according to any one of claims 1 to 4 or each water-based ink constituting the ink set according to claim 5 is individually stored, and for discharging the ink An inkjet recording apparatus comprising an inkjet head. An image is formed by using the water-based ink according to any one of claims 1 to 4 or each water-based ink constituting the ink set according to claim 5 to form an image on a recording material. Method.